Chronic ethanol and withdrawal effects on kainate receptor-mediated excitatory neurotransmission in the rat basolateral amygdala

Withdrawal (WD) anxiety is a significant factor contributing to continued alcohol abuse in alcoholics. This anxiety is extensive, long-lasting, and develops well after the obvious physical symptoms of acute WD. The neurobiological mechanisms underlying this prolonged WD-induced anxiety are not well understood. The basolateral amygdala (BLA) is a major emotional center in the brain and regulates the expression of anxiety. New evidence suggests that increased glutamatergic function in the BLA may contribute to WD-related anxiety following chronic ethanol exposure. Recent evidence also suggests that kainate-type ionotropic glutamate receptors are inhibited by intoxicating concentrations of acute ethanol. This acute sensitivity suggests potential (KA-R) contributions by these receptors to the increased glutamatergic function seen during chronic exposure. Therefore, we examined the effect of chronic intermittent ethanol (CIE) and WD on KA-R-mediated synaptic transmission in the BLA of Sprague-Dawley rats. Our study showed that CIE, but not WD, increased synaptic responses mediated by KA-Rs. Interestingly, both CIE and WD occluded KA-R-mediated synaptic plasticity. Finally, we found that BLA field excitatory postsynaptic potential responses were increased during CIE and WD via a mechanism that is independent of glutamate release from presynaptic terminals. Taken together, these data suggest that KA-Rs might contribute to postsynaptic increases in glutamatergic synaptic transmission during CIE and that the mechanisms responsible for the expression of KA-R-dependent synaptic plasticity might be engaged by chronic ethanol exposure and WD.     

Targeting dynorphin/kappa opioid receptor systems to treat alcohol abuse and dependence

This review represents the focus of a symposium that was presented at the “Alcoholism and Stress: A Framework for Future Treatment Strategies” conference in Volterra, Italy on May 3–6, 2011 and organized/chaired by Dr. Brendan M. Walker. The primary goal of the symposium was to evaluate and disseminate contemporary findings regarding the emerging role of kappa-opioid receptors (KORs) and their endogenous ligands dynorphins (DYNs) in the regulation of escalated alcohol consumption, negative affect and cognitive dysfunction associated with alcohol dependence, as well as DYN/KOR mediation of the effects of chronic stress on alcohol reward and seeking behaviors. Dr. Glenn Valdez described a role for KORs in the anxiogenic effects of alcohol withdrawal. Dr. Jay McLaughlin focused on the role of KORs in repeated stress-induced potentiation of alcohol reward and increased alcohol consumption. Dr. Brendan Walker presented data characterizing the effects of KOR antagonism within the extended amygdala on withdrawal-induced escalation of alcohol self-administration in dependent animals. Dr. Georgy Bakalkin concluded with data indicative of altered DYNs and KORs in the prefrontal cortex of alcohol dependent humans that could underlie diminished cognitive performance. Collectively, the data presented within this symposium identified the multifaceted contribution of KORs to the characteristics of acute and chronic alcohol-induced behavioral dysregulation and provided a foundation for the development of pharmacotherapeutic strategies to treat certain aspects of alcohol use disorders.     

Stress-related neuropeptides and alcoholism: CRH, NPY, and beyond

This article summarizes the proceedings of a symposium held at the conference on “Alcoholism and Stress: A Framework for Future Treatment Strategies” in Volterra, Italy, May 6-9, 2008. Chaired by Markus Heilig and Roberto Ciccocioppo, this symposium offered a forum for the presentation of recent data linking neuropetidergic neurotransmission to the regulation of different alcohol-related behaviors in animals and in humans. Dr. Donald Gehlert described the development of a new corticotrophin-releasing factor receptor 1 antagonist and showed its efficacy in reducing alcohol consumption and stress-induced relapse in different animal models of alcohol abuse. Dr. Andrey Ryabinin reviewed recent findings in his laboratory, indicating a role of the urocortin 1 receptor system in the regulation of alcohol intake. Dr. Annika Thorsell showed data supporting the significance of the neuropeptide Y receptor system in the modulation of behaviors associated with a history of ethanol intoxication. Dr. Roberto Ciccocioppo focused his presentation on the nociceptin/orphanin FQ (N/OFQ) receptors as treatment targets for alcoholism. Finally, Dr. Markus Heilig showed recent preclinical and clinical evidence suggesting that neurokinin 1 antagonism may represent a promising new treatment for alcoholism. Collectively, these investigators highlighted the significance of neuropeptidergic neurotransmission in the regulation of neurobiological mechanisms of alcohol addiction. Data also revealed the importance of these systems as treatment targets for the development of new medication for alcoholism.     

Support from Neurobiology for Spiritual Techniques for Anxiety: A Brief Review

Research in neurobiology supports use of spiritual techniques as a beneficial treatment for anxiety. Psychotherapy, including mindfulness CBT and meditation, has been shown to change brain structure. The amygdala—the brain structure responsible for processing emotion and anxiety—demonstrates plasticity, and the purpose of therapy may be to allow the cortex to establish more effective and efficient synaptic links with the amygdala. A main feature of spiritual approaches is changing one's focus of attention. Instead of worry, one focuses on peaceful thoughts, thoughts of helping others, etc. Research demonstrates that thought, meditation, and other manifestations of mind can alter the brain, sometimes in an enduring way. Few studies have addressed the neurobiological underpinnings of meditation. Limited evidence, however, suggests that brain changes occur during prolonged meditation and that meditation activates neural structures involved in attention and control of the autonomic nervous system.     

AMPAR-mediated synaptic transmission in the CA1 hippocampal region of neonatal rats: unexpected resistance to repeated ethanol exposure

α-Amino-3-hydroxyl-5-methyl-4-isoxazole-propionate glutamatergic receptors (AMPAR) mediate most of the fast excitatory synaptic transmission in mature neurons. In contrast, a number of developing synapses do not express AMPARs; these are gradually acquired in an activity-driven manner during the first week of life in rats, which is equivalent to the third trimester of human pregnancy. Neuronal stimulation has been shown to drive high conductance Ca²⁺-permeable AMPARs into the synapse, strengthening glutamatergic synaptic transmission. Alterations in this process could induce premature stabilization or inappropriate elimination of newly formed synapses and contribute to the hippocampal abnormalities associated with fetal alcohol spectrum disorder. Previous studies from our laboratory performed with hippocampal slices from neonatal rats showed that acute ethanol exposure exerts potent stimulant effects on CA1 and CA3 neuronal networks. However, the impact of these in vitro actions of acute ethanol exposure is unknown. Here, we tested the hypothesis that repeated in vivo exposure to ethanol strengthens AMPAR-mediated neurotransmission in the CA1 region by means of an increase in synaptic expression of Ca²⁺-permeable AMPARs. We exposed rats to ethanol vapor (serum ethanol concentration ∼40 mM) or air for 4 h/day from postnatal day (P) 2-6. In brain slices prepared at P4-6, we found no significant effect of ethanol exposure on input-output curves for AMPAR-mediated field excitatory postsynaptic potentials (fEPSPs), the contribution of Ca²⁺-permeable AMPARs to these fEPSPs, or the acute effect of ethanol on fEPSP amplitude. These results suggest that homeostatic plasticity mechanisms act to maintain glutamatergic synaptic strength and ethanol sensitivity in response to repeated developmental ethanol exposure.     

Effects of chronic ethanol exposure on neurophysiological responses to corticotropin-releasing factor and neuropeptide Y.

Stress has been reported to influence ethanol consumption and relapse in abstinent alcoholics. The present study examined if prolonged alterations in neurophysiological responses to corticotropin-releasing factor (CRF) and neuropeptide Y (NPY), peptides known to influence stress responses, would persist during protracted ethanol abstinence. Male Wistar rats were chronically exposed to ethanol vapour (EtOH group) or air (control group) for 6 weeks. Upon removal from the vapour chambers, recording electrodes were implanted in the cortex and amygdala. The effects of intracerebroventricular infusions of CRF and NPY on electroencephalogram (EEG) and event-related potentials (ERPs) were then assessed 10-15 weeks after withdrawal from ethanol. Following abstinence from ethanol, the EtOH group displayed increased power in the 6-8 Hz frequency range and increased stability in the cortical EEG. In addition, in the EtOH group the amplitude of the P2 ERP component in the frontal cortex was decreased and the latency of the P3 ERP component in the parietal cortex was delayed, compared to the control group during baseline recording conditions. The EtOH group was also more responsive to CRF and NPY. CRF significantly increased cortical power (6-8 Hz) and increased cortical EEG stability in the EtOH group, compared to controls. Additionally, NPY significantly decreased the amplitude of the N1 ERP component in the amygdala of the EtOH group, but not in the control group. This enhanced sensitivity to CRF and NPY following chronic ethanol exposure and abstinence suggests that these peptidergic systems may play a role in the symptomatology of the prolonged abstinence syndrome.     

RDX binds to the GABA(A) receptor-convulsant site and blocks GABA(A) receptor-mediated currents in the amygdala: a mechanism for RDX-induced seizures

Background

Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) is a high-energy, trinitrated cyclic compound that has been used worldwide since World War II as an explosive in both military and civilian applications. RDX can be released in the environment by way of waste streams generated during the manufacture, use, and disposal of RDX-containing munitions and can leach into groundwater from unexploded munitions found on training ranges. For > 60 years, it has been known that exposure to high doses of RDX causes generalized seizures, but the mechanism has remained unknown.

Objective

We investigated the mechanism by which RDX induces seizures.

Methods and results

By screening the affinity of RDX for a number of neurotransmitter receptors, we found that RDX binds exclusively to the picrotoxin convulsant site of the γ-aminobutyric acid type A (GABA_A) ionophore. Whole-cell in vitro recordings in the rat basolateral amygdala (BLA) showed that RDX reduces the frequency and amplitude of spontaneous GABA_A receptor–mediated inhibitory postsynaptic currents and the amplitude of GABA-evoked postsynaptic currents. In extracellular field recordings from the BLA, RDX induced prolonged, seizure-like neuronal discharges.

Conclusions

These results suggest that binding to the GABA_A receptor convulsant site is the primary mechanism of seizure induction by RDX and that reduction of GABAergic inhibitory transmission in the amygdala is involved in the generation of RDX-induced seizures. Knowledge of the molecular site and the mechanism of RDX action with respect to seizure induction can guide therapeutic strategies, allow more accurate development of safe thresholds for exposures, and help prevent the development of new explosives or other munitions that could pose similar health risks.     

Targeted Approaches for In Situ Gut Microbiome Manipulation

The 2019 Dudrick Research Symposium, entitled “Targeted Approaches for In Situ Gut Microbiome Manipulation,” was held on March 25, 2019, at the American Society for Parenteral and Enteral Nutrition (ASPEN) 2019 Nutrition Science & Practice Conference in Phoenix, AZ. The Dudrick Symposium honors the many pivotal and innovative contributions to the development and advancement of parenteral nutrition (PN) made by Dr Stanley J. Dudrick, physician scientist, academic leader, and a founding member of ASPEN. As the 2018 recipient of the Dudrick award, Dr Gail Cresci organized and chaired the symposium. The symposium addressed the evolving field of nutrition manipulation of the gut microbiome as a means to mitigate disease and support health. Presentations focused on (1) the role of prebiotics as a means to beneficially support gut microbiome composition and function and health; (2) designer synbiotics targeted to support metabolic by-products altered by ethanol exposure and microbial effectors that manipulate host metabolic outcomes; and, lastly, (3) types of intervention designs used to study diet–gut microbiome interactions in humans and a review of findings from recent interventions, which tested the effects of diet on the microbiome and the microbiome's effect on dietary exposures. New molecular techniques and multiomic approaches have improved knowledge of the structure and functional activity of the gut microbiome; however, challenges remain in establishing causal relationships between changes in the gut microbial–community structure and function and health outcomes in humans.     

Localization of brain 5α-reductase messenger RNA in mice selectively bred for high chronic alcohol withdrawal severity

Several lines of evidence suggest that fluctuations in endogenous levels of the γ-aminobutyric acid (GABA)ergic neurosteroid allopregnanolone (ALLO) represent one mechanism for regulation of GABAergic inhibitory tone in the brain, with an ultimate impact on behavior. Consistent with this idea, there was an inverse relationship between ALLO levels and symptoms of anxiety and depression in humans and convulsive activity in rodents during alcohol withdrawal. Our recent studies examined the activity and expression of 5α-reductase (Srd5a1), the rate-limiting enzyme in the biosynthesis of ALLO, during alcohol withdrawal in mice selectively bred for high chronic alcohol withdrawal (Withdrawal Seizure-Prone [WSP]) and found that Srd5a1 was downregulated in the cortex and hippocampus over the time course of dependence and withdrawal. The purpose of the present studies was to extend these findings and more discretely map the regions of Srd5a1 expression in mouse brain using radioactive in situ hybridization in WSP mice that were ethanol naïve, following exposure to 72 h ethanol vapor (dependent) or during peak withdrawal. In naïve animals, expression of Srd5a1 was widely distributed throughout the mouse brain, with highest expression in specific regions of the cerebral cortex, hippocampus, thalamus, hypothalamus, and amygdala. In dependent animals and during withdrawal, there was no change in Srd5a1 expression in cortex or hippocampus, which differed from our recent findings in dissected tissues. These results suggest that local Srd5a1 mRNA expression in WSP brain may not change in parallel with local ALLO content or withdrawal severity.     

Developmental changes in the acute ethanol sensitivity of glutamatergic and GABAergic transmission in the BNST

Glutamatergic and GABAergic transmission undergo significant changes during adolescence. Receptors for both of these transmitters (NMDAR, and GABA_A) are known to be key targets for the acute effects of ethanol in adults. The current study set out to investigate the acute effects of ethanol on both NMDAR-mediated excitatory transmission and GABAergic inhibitory transmission within the bed nucleus of the stria terminalis (BNST) across age. The BNST is an area of the brain implicated in the negative reinforcing properties associated with alcohol dependence, and the BNST plays a critical role in stress-induced relapse. Therefore, assessing the developmental regulation of ethanol sensitivity in this key brain region is important to understanding the progression of ethanol dependence. To do this, whole-cell recordings of isolated NMDAR-evoked excitatory postsynaptic currents (eEPSCs) or evoked GABAergic inhibitory postsynaptic currents (eIPSCs) were performed on BNST neurons in slices from 4- or 8-week-old male C57BL/6J mice. Ethanol (50 mm) produced greater inhibition of NMDAR–eEPSCs in adolescent mice than in adult mice. This enhanced sensitivity in adolescence was not a result of shifts in function of the GluN2B subunit of the NMDAR, measured by Ro25-6981 inhibition and decay kinetics measured across age. Adolescent mice also exhibited greater ethanol sensitivity of GABAergic transmission, as ethanol (50 mm) enhanced eIPSCs in the BNST of adolescent but not adult mice. Collectively, this work illustrates that a moderate dose of ethanol produces greater inhibition of transmission in the BNST (through greater excitatory inhibition and enhancement of inhibitory transmission) in adolescents compared to adults. Given the role of the BNST in alcohol dependence, these developmental changes in acute ethanol sensitivity could accelerate neuroadaptations that result from chronic ethanol use during the critical period of adolescence.     

The effects of acute and chronic ethanol exposure on presynaptic and postsynaptic gamma-aminobutyric acid (GABA) neurotransmission in cultured cortical and hippocampal neurons

Decades after ethanol was first described as a gamma-aminobutyric acid (GABA) mimetic, the precise mechanisms that produce the acute effects of ethanol and the physiological adaptations that underlie ethanol tolerance and dependence remain unclear. Although a substantial body of evidence suggests that ethanol acts on GABAergic neurotransmission to enhance inhibition in the central nervous system, the precise mechanisms underlying the physiological effects of both acute and chronic ethanol exposure are still under investigation. We have used in vitro ethanol exposure followed by recording of miniature inhibitory postsynaptic currents (mIPSCs) to determine whether acute or chronic ethanol exposure directly alters synaptic GABA_A receptor (GABA_AR) function or GABA release in cultured cortical and hippocampal neurons. Acute ethanol exposure slightly increased the duration of mIPSCs in hippocampal neurons but did not alter mIPSC kinetics in cortical neurons. Acute ethanol exposure did not change mIPSC frequency in either hippocampal or cortical neurons. One day of chronic ethanol exposure produced a transient decrease in mIPSC duration in cortical neurons but did not alter mIPSC kinetics in hippocampal neurons. Chronic ethanol exposure did not change mIPSC frequency in either hippocampal or cortical neurons. Chronic ethanol exposure also did not produce substantial cross-tolerance to a benzodiazepine in either hippocampal or cortical neurons. The results suggest that ethanol exposure in vitro has limited effects on synaptic GABA_AR function and action potential-independent GABA release in cultured neurons and that ethanol exposure in cultured cortical and hippocampal neurons may not reproduce all the effects that occur in vivo and in acute brain slices.     

Antagonism of corticotropin-releasing factor attenuates the enhanced responsiveness to stress observed during protracted ethanol abstinence.

One of the most critical attributes of chronic abstinence from alcohol is a state of anxiety, which can lead to mood disturbances and negative affect that can last for months or even years in alcoholics. Within hours after their final exposure to ethanol in experimental conditions, laboratory animals also exhibit an anxiety-like state. This state is accompanied by an enhanced stress response and can persist for weeks after withdrawal. One possible mechanism underlying these behavioral changes observed weeks after withdrawal is increased corticotropin-releasing factor (CRF) activity. In the present study, we sought to examine the role of CRF in the regulation of behavior in the elevated plus-maze during protracted abstinence by using intracerebroventricular administration of the CRF receptor antagonist [D-Phe(12),Nle(21,38),CalphaMeLeu(37)]rCRF((12-41)) (D-Phe-CRF((12-41))). Rats were surgically implanted with a guide cannula aimed at the lateral ventricles and subsequently fed a nutritionally complete ethanol [10% (vol./vol.)] or control liquid diet for 21 days. Rats were further divided into groups receiving microinjections of D-Phe-CRF((12-41)) or vehicle and 15 min of restraint stress, or D-Phe-CRF((12-41)) or vehicle and no restraint. Six weeks after removal of the liquid diet, rats were injected and then placed in a restraint tube or returned to their home cages for 15 min before testing in the elevated plus-maze. Rats with a history of ethanol dependence explored the open arms of the plus-maze significantly less when exposed to restraint stress compared with findings for all other groups, an effect attenuated by pretreatment with D-Phe-CRF((12-41)). Results of the current experiment demonstrated that continuous exposure to ethanol over a 3-week period leads to an increased behavioral responsiveness to stress, which seems to be regulated by CRF.     

Urocortins: CRF's siblings and their potential role in anxiety,depression and alcohol drinking behavior

It is widely accepted that stress, anxiety, depression and alcohol abuse-related disorders are in large part controlled by corticotropin-releasing factor (CRF) receptors. However, evidence is accumulating that some of the actions on these receptors are mediated not by CRF, but by a family of related Urocortin (Ucn) peptides Ucn1, Ucn2 and Ucn3. The initial narrow focus on CRF as the potential main player acting on CRF receptors appears outdated. Instead it is suggested that CRF and the individual Ucns act in a complementary and brain region-specific fashion to regulate anxiety-related behaviors and alcohol consumption. This review, based on a symposium held in 2011 at the research meeting on “Alcoholism and Stress” in Volterra, Italy, highlights recent evidence for regulation of these behaviors by Ucns. In studies on stress and anxiety, the roles of Ucns, and in particular Ucn1, appear more visible in experiments analyzing adaptation to stressors rather than testing basal anxiety states. Based on these studies, we propose that the contribution of Ucn1 to regulating mood follows a U-like pattern with both high and low activity of Ucn1 contributing to high anxiety states. In studies on alcohol use disorders, the CRF system appears to regulate not only dependence-induced drinking, but also binge drinking and even basal consumption of alcohol. While dependence-induced and binge drinking rely on the actions of CRF on CRFR1 receptors, alcohol consumption in models of these behaviors is inhibited by actions of Ucns on CRFR2. In contrast, alcohol preference is positively influenced by actions of Ucn1, which is capable of acting on both CRFR1 and CRFR2. Because of complex distribution of Ucns in the nervous system, advances in this field will critically depend on development of new tools allowing site-specific analyses of the roles of Ucns and CRF.     

Effects of prolonged ethanol vapor exposure on forced swim behavior, and neuropeptide Y and corticotropin-releasing factor levels in rat brains

Depressive symptoms in alcohol-dependent individuals are well-recognized and clinically relevant phenomena. The etiology has not been elucidated although it is clear that the depressive symptoms may be alcohol independent or alcohol induced. To contribute to the understanding of the neurobiology of chronic ethanol use, we investigated the effects of chronic intermittent ethanol vapor exposure on behaviors in the forced swim test (FST) and neuropeptide Y (NPY) and corticotropin-releasing factor (CRF) levels in specific brain regions. Adult male Wistar rats were subjected to intermittent ethanol vapor (14 h on/10 h off) or air exposure for 2 weeks and were then tested at three time points corresponding to acute withdrawal (8-12 h into withdrawal) and protracted withdrawal (30 and 60 days of withdrawal) in the FST. The behaviors that were measured in the five-min FST consisted of latency to immobility, swim time, immobility time, and climbing time. The FST results showed that the vapor-exposed animals displayed depressive-like behaviors; for instance, decreased latency to immobility in acute withdrawal and decreased latency to immobility, decreased swim time and increased immobility time in protracted withdrawal, with differences between air- and vapor-exposed animals becoming more pronounced over the 60-day withdrawal period. NPY levels in the frontal cortex of the vapor-exposed animals were decreased compared with the control animals, and CRF levels in the amygdala were correlated with increased immobility time. Thus, extended ethanol vapor exposure produced long-lasting changes in FST behavior and NPY levels in the brain.     

SB242084, flumazenil, and CRA1000 block ethanol withdrawal-induced anxiety in rats.

Anxiety-like behaviors are integral features of withdrawal from chronic ethanol exposure. In the experiments in the current study, we tested the hypothesis that anxiety can be regulated independently of other withdrawal signs and thus may be responsive to selective pharmacological agents. For 17 days, rats were fed ethanol (8-12 g/kg/day) in a liquid diet. Between 5 and 6 h after cessation of ethanol treatment, rats were tested in either the social interaction or plus-maze test of anxiety-like behavior after treatment with drugs hypothesized to have anxiolytic action. SB242084, flumazenil, and CRA1000-antagonists for 5-hydroxytryptamine (serotonin) (5-HT) 2C (5-HT(2C)), benzodiazepine, and corticotropin-releasing factor type 1 (CRF(1)) receptors, respectively-attenuated decreased social interaction without concomitant effects on activity measures. In contrast, ifenprodil, MDL 72222, and zolpidem-antagonists for N-methyl-d-aspartate (NMDA) and 5-HT(3) receptors, and agonist for benzodiazepine type 1 receptors, respectively-did not share this effect. Results for SB242084, flumazenil, and ifenprodil in the elevated plus-maze test were comparable to those in the social interaction test. These results support the suggestion that multiple neuronal systems (CRF(1), 5-HT(2C), and benzodiazepine receptors) contribute to the ethanol withdrawal sign of decreased social interaction. Furthermore, the selective effects of pharmacological agents on social interaction seem to indicate that this behavior can be dissociated from other signs. Because anxiety may be a complicating factor in alcohol withdrawal and relapse, future studies of this type are needed to provide focus for the effort to define selective and novel antianxiety agents for these disorders.     

The role of neuroactive steroids in ethanol/stress interactions: proceedings of symposium VII at the Volterra conference on alcohol and stress, May 2008

This report summarizes the proceedings of the symposium VII on the role of neuroactive steroids in stress/alcohol interactions. The production of GABAergic neuroactive steroids, including (3α,5α)-3-hydroxypregnan-20-one and (3α,5α)-3,21-dihydroxypregnan-20-one is a consequence of both acute stress and acute ethanol exposure. Acute, but not chronic ethanol administration elevates brain levels of these steroids and enhances GABA_A receptor activity. Neuroactive steroids modulate acute anticonvulsant effects, sedation, spatial memory impairment, anxiolytic-like, antidepressant-like, and reinforcing properties of ethanol in rodents. Furthermore, these steroids participate in the homeostatic regulation of the hypothalamic-pituitary-adrenal axis. Therefore, it is not surprising that neuroactive steroids are involved in ethanol/stress interactions. Nevertheless, the interactions are complex and not well understood. This symposium addressed the role of neuroactive steroids in both stress and alcohol responses and their interactions. Professor Giovanni Biggio of the University of Cagliari, Italy presented the effects of juvenile isolation stress on neuroactive steroids, GABA_A receptor expression, and ethanol sensitivity. Professor Howard Becker of the Medical University of South Carolina, USA presented evidence for neuroactive steroid involvement in ethanol dependence and drinking behavior. Professor Patrizia Porcu of the University of North Carolina, USA described a potential neuroactive steroid biomarker that may predict heavy drinking in monkeys and mice. These presentations provide a framework for new theories on the nature of ethanol/stress interactions that may be amenable to therapeutic interventions.     

Anxiolytic effects of sesamin in mice with chronic inflammatory pain

Objective: Sesamin is known for its role in antioxidant, antiproliferative, antihypertensive, and neuroprotective activities. However, little is known about the role of sesamin in the development of emotional disorders. Here we investigated persistent inflammatory pain hypersensitivity and anxiety-like behaviors in the mouse suffering chronic pain.

Methods: Chronic inflammatory pain was induced by hind paw injection of complete Freund's adjuvant (CFA). Levels of protein were detected by Western blot.

Results: Administration of sesamin could induce anxiolytic activities but had no effect on analgesia. In the basolateral amygdala, a structure involving the anxiety development, sesamin attenuated the up-regulation of NR2B-containing N-methyl-d-aspartate receptors, GluR1 subunit of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor as well as phosphorylation of GluR1 at Ser831 (p-GluR1-Ser831), and Ca²⁺/calmodulin-dependent protein kinase II (CaMKII-alpha) in the hind paw CFA-injected mice. In the same model, we found that the sesamin blocked the down-regulation of gamma-aminobutyric acid A (GABA_A-alpha-2) receptors.

Conclusion: Our findings show that sesamin reduces anxiety-like behaviors induced by chronic pain at least partially through regulating the GABAergic and glutamatergic transmission in the amygdala of mice.     

Repeated third trimester-equivalent ethanol exposure inhibits long-term potentiation in the hippocampal CA1 region of neonatal rats

Developmental ethanol exposure damages the hippocampus, causing long-lasting learning and memory deficits. Synaptic plasticity mechanisms (e.g., long-term potentiation [LTP]) contribute to synapse formation and refinement during development. We recently showed that acute ethanol exposure inhibits glutamatergic synaptic transmission and N-methyl-d-aspartate receptor (NMDAR)-dependent LTP in the CA1 hippocampal region of postnatal day (P)7-9 rats. The objective of this study was to further characterize the effect of ethanol on LTP in the developing CA1 hippocampus during the third trimester equivalent. To more closely model human ethanol exposure during this period, rat pups were exposed to ethanol vapor (2 or 4.5 g/dL in air, serum ethanol concentrations = 96.6-147.2 or 322-395.6 mg/dL) from P2-9 (4 h/d). Brain slices were prepared immediately after the end of the 4-h exposure on P7-9 and extracellular electrophysiological recordings were performed 1-7 h later under ethanol-free conditions to model early withdrawal. LTP was not different than group-matched controls in the 96.6-147.2 mg/dL group; however, it was impaired in the 322-395.6 mg/dL group. Neither α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate receptor (AMPAR)/NMDAR function nor glutamate release were affected in the 322-395.6 mg/dL ethanol exposure group. These data suggest that repeated in vivo exposure to elevated ethanol doses during the third trimester-equivalent period impairs synaptic plasticity, which may alter maturation of hippocampal circuits and ultimately contribute to the long-lasting cognitive deficits associated with fetal alcohol spectrum disorders.